1. Field of the Invention
The present invention relates to an improved process for the preparation of sodium fluoroalcoholates, and, more especially, to an improved process for the preparation of sodium fluoroalcoholates by reacting the corresponding fluoroalcohols with sodium methanolate, while selectively trapping the methanol of reaction.
2. Description of the Prior Art
There are numerous applications for the sodium fluoroalcoholates which are known to this art. For example, poly(fluoroalkoxy)phosphazenes may be prepared by reacting sodium fluoroalcoholates with polydichlorophosphazene, according to the reaction scheme: ##STR1## (compare, e.g., U.S. Pat. No. 3,515,688).
Various methods have been proposed to the art for preparing sodium fluoroalcoholates, by an alkalinization reaction using sodium or a sodium compound, such reaction hereinafter being designated sodionation for the sake of simplicity.
Thus, U.S. Pat. No. 3,702,833 describes the heating of fluoroalcohols with metallic sodium, under reflux, in tetrahydrofuran (THF). Depending on the particular alcohol used, this reaction entails varying degrees of degradation, resulting in the formation of sodium fluoride, and the basicity of the reaction medium is less than would be expected, considering the amount of sodium used.
U.S. Pat. No. 4,357,458 describes sodionation using sodium hydroxide, characterized by a displacement of the reaction equilibrium by distillation of a hydrocarbon which entrains the water formed during the reaction. This technique requires a long reaction time (generally greater than 20 hours).
U.S. Pat. Nos. 4,568,779 and 4,593,129 feature dispersing the sodium in finely divided form in a cycloalkane prior to contacting it with a fluoroalcohol. In this manner, the reactivity of the sodium is increased and it is thus possible to conduct the reaction at a low temperature. However, this process requires the use of a reactor which is equipped with a system for atomizing sodium, another refrigerated reactor for carrying out the sodionation, and the substitution reaction itself is carried out in yet a third apparatus.
It will be appreciated that even using atomized sodium, the reaction remains of long duration when it is carried out at low temperature.